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Date: Wed, 11 Feb 2015 13:01:56 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Andy Lutomirski <luto@amacapital.net>,
        Denys Vlasenko <dvlasenk@redhat.com>
CC: Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Frederic Weisbecker <fweisbec@gmail.com>, X86 ML <x86@kernel.org>,
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        Kees Cook <keescook@chromium.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 02/11] x86: code shrink in paranoid_exit
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On 02/11/2015 12:36 PM, Andy Lutomirski wrote:
> 
> This is sort of a reply to the wrong thread, but wouldn't it be nicer
> if we could pop a bunch of regs instead of using mov followed by add?
> (Yes, this could be a followup, but it could be easier to spot now by
> changing macros like RESTORE_XYZ.)
> 

As far as I recall, it was an optimization for the Pentium 4 and
possibly K8.  At this point, most CPUs have stack engines so push/pop
may be faster or at least the same speed.  It would be nice to
microbenchmark.

	-hpa